EP2416507B1

EP2416507B1 - Method and system for antenna calibration

Info

Publication number: EP2416507B1
Application number: EP09842520.0A
Authority: EP
Inventors: Chenhong Lu
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2009-04-03
Filing date: 2009-11-30
Publication date: 2018-04-11
Anticipated expiration: 2029-11-30
Also published as: JP2012523140A; SI2416507T1; CN101854323A; WO2010111864A1; EP2416507A1; CN101854323B; JP5686792B2; EP2416507A4

Description

Technical Field

The present invention relates to the field of communication, and especially, to a method and system for antenna calibration.

Background of the Related Art

To date, in order to reduce the co-channel interference, increase the cell edge throughput and coverage in the orthogonal frequency division multiplexing-time division duplex (OFDM-TDD) system, multi-antenna beam forming technology with relatively small distance between the array elements is introduced in the eNodeB. In order to guarantee the accuracy and reliability of the forming, the antenna array must be calibrated to reduce the error in amplitude and phase in each channel of the array.
In the prior art, the antenna calibration technology in the orthogonal frequency division multiplexing (OFDM) system is mainly: after receiving the frequency domain pilot sequence transmitted by each transmitting antenna, jointly estimating the frequency domain response of each transmitting antenna channel at the receiving end, and then compensating the difference in the frequency domain responses of different reflecting antennae, so as to achieve the frequency domain calibration of transmitting electronic channel of each transmitting antenna; in addition, when simultaneously calibrating several transmitting channels, the inter-channel interference can be reduced by using a way of frequency division or code division.
However, since the channel used in the antenna calibration is the same as that used in the communication system, in order to not affect the normal operation of the communication system, the calibration detection pilot signal should be transmitted when there is no communication data transmitted. According to the time slot structure of the time division duplex (TDD), the calibration detection pilot signal is generally selected to be transmitted in the guard period (GP) between the downlink pilot time slot (DwPTS) and the Uplink Pilot Time Slot (UpPTS). However, echoes of the downlink signal in the DwPTS might interfere with the calibration signal in the GP, thus affect the calibration effect. In the prior art, cyclic prefix is added to reduce the interference and influence due to the channel tailing, and select the length of the cyclic prefix to reduce the influence of the calibration pilot symbol on the downlink pilot echo, and the longer a cyclic prefix is added, the more likely the effective calibration pilot symbol will be located in the rear of the idle time slot, thus by reasonably selecting the length of the cyclic prefix, the interference can be located only in the cyclic prefix signal.
The abovementioned processing method only considers reducing the interference from the DwPTS, but does not consider that increasing the length of the cyclic prefix might extend the effective calibration pilot signal to the UpPTS, which not only affects the normal uplink communication, but also reduces the calibration precision. Meanwhile, when there is a random access signal that is transmitted in advance, there is mutual interference between the calibration pilot signal and the random access signal.
The document CN101188448A discloses an intelligent antenna calibration method, as well as the device and the system thereof, and estimates the frequency response of the corresponding sub carrier wave position of each transmitting antenna and the channel impact response length of each transmitting antenna according to the received pilot symbols; the maximum value of the channel impact response length and the frequency response of each transmitting antenna are used for the interpolation on the positions of the sub carrier wave without the estimation of frequency response; according to the interpolated frequency response, the compensation coefficient of each transmitting antenna is worked out, and each transmitting antenna gets compensated correspondingly according to the compensation coefficient so as to lead the frequency response of each transmitting channel to be identical.
The document US2007037519A1 discloses an apparatus and method for calibrating transmission paths in a multicarrier communication system using multiple antennas. In the transmission path calibrating apparatus, a calibration processor generates reference signal to estimate distortions in phase and amplitude in transmission paths, allocates the generated reference signals to subcarriers which are different in each of the transmission paths, and calculates calibration vectors for the transmission paths using the generated reference signals and received reference signals received through the transmission paths. A baseband module IFFT-processes the generated reference signals allocated to the subcarriers and send the IFFT signals in the transmission paths.
The document US2008310529A1 discloses a radio transmitting apparatus includes a calibration reference signal generator for generating a calibrated reference signal for each of the subcarriers to be calibrated, a subcarrier modulator for modulating the calibration reference signal with the subcarrier, a radio transmitter for frequency-convert-transmission signals in a radio frequency band, a radio receiver for frequency-converting the transmission signal in the radio frequency band supplied from the radio transmitter, into a baseband signal, a calibration coefficient measurer for calculating a calibration coefficient from the baseband signal output from the radio receiver, and a calibration coefficient multiplier for multiplying a transmission signal for each of the subcarriers and each of the antenna elements, by the calculated calibration coefficient.

Summary of the Invention

The present invention is proposed since the calibration detection pilot signal interferes with the normal communication in the communication system in the prior art; therefore, the main purpose of the present invention is to provide a method and system for antenna calibration, so as to solve the abovementioned problem in the prior art.
In order to achieve the purpose of the present invention, the present invention provides a method for antenna calibration according to claim 1. Preferably, the transmitting end grouping the sub-carrier frequency points in the transmitting antenna specifically comprises: the transmitting end groups the sub-carrier frequency points in at least one transmitting antenna.
Preferably, when there are at least two transmitting antennae, after the transmitting end sends the time domain signal to the receiving end, the abovementioned method further comprises: the receiving end superimposes the time domain transmitting signals into one receiving calibration channel to receive.
Preferably, the transmitting end groups the sub-carrier frequency points in the transmitting antennae, and it specifically comprises: determining the number of groups of grouping the sub-carrier frequency points; grouping each sub-carrier frequency point in sequence in the order from the first group to the last group according to the frequency size of the sub-carrier frequency point, and if the number of sub-carrier frequency points is greater than the number of groups, allocating the rest sub-carrier frequency points in sequence from the first group to the last group again; determining the number of sub-carrier frequency points in each group.
Preferably, the total number of the sub-carrier frequency points can be exactly divided by the number of the groups.
Preferably, the number of groups is 4 or 8.
Preferably, the transmitting end determines the frequency domain calibration pilot signal of the transmitting antenna according to the grouping, and the procedure specifically comprises: the transmitting end determines the basic sequence according to the number of sub-carrier frequency points in each group, and determines the frequency domain calibration pilot signal of the transmitting antenna according to the basic sequence.
Preferably, when carrying out multi-channel simultaneous transmission calibration, the abovementioned method also comprises: the transmitting end uses a way of code division multiplexing to determine the frequency domain calibration pilot signal of each calibration channel.
Preferably, the pilot sequence of the code division multiplexing is Zadoff chu basic sequence. The transmitting end acquires the time domain integrated calibration pilot signal according to the frequency domain calibration pilot signal, and uses the time domain integrated calibration pilot signal to construct the time domain transmitting signal and sends it to the receiving end, and it specifically comprises: the transmitting end maps the frequency domain calibration pilot signal to the corresponding grouped sub-carrier frequency points, and fills locations of the rest unmapped sub-carrier frequency points with zero value to acquire the frequency domain signal of the transmitting antenna; the transmitting end coverts the frequency domain signal of the transmitting antenna to the time domain integrated calibration pilot signal of the transmitting antenna; the transmitting end segments the time domain integrated calibration pilot signal of the transmitting antenna according to the number of groups, and selects any segment of signal as the effective calibration signal; the transmitting end carries out an operation of filling zeros before and after the effective calibration signal to construct the time domain transmitting signal of the transmitting antenna; the transmitting end sends the time domain transmitting signal to the receiving end.
Preferably, the receiving end recovered the time domain integrated calibration pilot signal according to the received time domain transmitting signal, and it comprises: the receiving end carries out an operation of removing the zeros on the time domain transmitting signal to acquire the effective calibration signal, and the receiving end carries out recovery processing on the effective calibration signal to acquire the time domain integrated calibration pilot signal.
Preferably, the receiving end acquiring the frequency domain response of each group according to the recovered time domain integrated calibration pilot signal comprises: the receiving end converts the recovered time domain integrated calibration pilot signal to a frequency domain signal; the receiving end acquires the frequency domain response of each group in the calibration channel according to the frequency domain pilot of each group in the calibration channel.
Preferably, the receiving end acquiring the frequency domain response of each group according to the recovered time domain integrated calibration pilot signal further comprises: after superimposing the recovered time domain integrated calibration pilot signal of each group, the receiving end performs fast Fourier Transform on the signal to acquire the frequency domain signal, and estimates the frequency response of the corresponding sub-carriers of each group in the calibration channel according to the frequency domain pilot of each group in the calibration channel; or, the receiving end carries out fast Fourier transform on the recovered time domain integrated calibration pilot signal of each group to acquire the frequency domain signal of each group, and estimates the frequency response of the corresponding sub-carrier of each group according to the frequency domain pilot of each group in the calibration channel.
Preferably, the receiving end acquiring the frequency domain responses of all sub-carrier frequency points according to the frequency domain response of each group in the calibration channel comprises: the receiving end directly combines the frequency domain response of the frequency point corresponding to each sub-carrier frequency point group for each calibration channel to acquire the frequency domain responses of all sub-carriers; or, for each calibration channel, the receiving end uses the determined frequency response to interpolate the sub-carrier frequency points without frequency response for the frequency response of sub-carrier frequency points in each group, and averages several frequency responses corresponding to each sub-carrier frequency point to acquire the frequency domain responses of all sub-carriers; or, the receiving end selects the frequency response of sub-carrier frequency points in one group for each calibration channel and uses the determined frequency response to interpolate the sub-carrier frequency points without frequency responses to acquire the frequency domain responses of all sub-carriers.
Preferably, after the receiving end acquiring the frequency domain responses of all sub-carriers according to the frequency domain response of each group in the calibration channel, the abovementioned method also comprises: the receiving end repeats the operation of acquiring the frequency domain response of each group and the frequency domain responses of all sub-carriers to acquire the several frequency domain responses of all sub-carriers; the receiving end averages the several frequency domain responses of all sub-carriers to acquire a mean value of the several frequency domain responses of all sub-carriers.
Preferably, the receiving end determining the compensation coefficient of the calibration channel according to the frequency domain response of all sub-carriers comprises: the receiving end determines the compensation coefficient of the calibration channel according to the mean value.
Preferably, after the receiving end determining the compensation coefficient of the calibration channel according to the mean value, the abovementioned method also comprises: the receiving end correspondingly compensates the calibration channel according to the compensation coefficient.
In order to achieve the abovementioned purpose, the other aspect of the present invention is to provide a system for antenna calibration according to claim 17. The transmitting end comprises: a frequency domain calibration pilot sequence generation unit used to group the sub-carrier frequency points of at least one transmitting antenna and determine the frequency domain calibration pilot signals of at least one transmitting antenna according to the grouping; a frequency domain calibration pilot sequence mapping unit, used to map the frequency domain calibration pilot signal to the corresponding grouped sub-carrier frequency points to acquire the frequency domain signals of at least one transmitting antenna; a first conversion unit, used to covert the frequency domain signal to the time domain integrated calibration pilot signals of at least one transmitting antenna; a time domain transmitting signal generation unit ,used to segment the time domain integrated calibration pilot signal, and select any segment of signal as the effective calibration signal and construct the time domain transmitting signals of at least one transmitting antenna.
The receiving end comprises: a time domain calibration pilot recovery unit, used to restore the time domain transmitting signal to the time domain integrated calibration pilot signal; a second conversion unit, used to covert the time domain integrated calibration pilot signal to the frequency domain signal; a sub-carrier frequency response estimation unit, used to determine the frequency domain response of each group according to the frequency domain signal; a channel frequency response synthesizing unit, used to determine the frequency domain responses of all sub-carrier frequency points in at least one calibration channel according to the frequency domain response of each group; a channel frequency response smoothing unit, used to carry out an average operation on frequency domain responses of all sub-carrier frequency points in at least one calibration channel which are acquired many times, to acquire the mean value of frequency domain responses of all sub-carriers of at least one calibration channel; a compensation coefficient determination unit, used to determine the compensation coefficients of at least one calibration channel according to the mean value of several calibration channels.
With the technical scheme of the present invention, by grouping the sub-carriers to construct a regular time domain calibration pilot signal, the calibration pilot time domain transmitting time length can be reduced, so as to solve the problem that the calibration detection pilot signal interferes with the normal communication of the communication system in the prior art, so that the transmission of the antenna calibration pilot signal can avoid the influence of the DwPTS and the UpPTS and improve the calibration estimation precision without affecting the normal communication.

Brief Description of Drawings

FIG. 1 is a flow chart of the method for antenna calibration in accordance with an example of the present invention;
FIG. 2 is a schematic diagram of the transmitting end grouping the sub-carrier frequency points in each transmitting antenna in accordance with an example of the present invention;
FIG. 3 is a flow chart of the detailed processing in the method for antenna calibration in accordance with an example of the present invention;
FIG. 4 is a block diagram of the system for antenna calibration in accordance with an example of the present invention.

Preferred Embodiments of the Present Invention

In order to solve the problem that the calibration detection pilot signal interferes with the normal communication of the communication system in the prior art, the present invention provides a method and system for antenna calibration, and in the technical scheme of the present invention, regularly group the sub-carrier frequency points of the transmitting antenna, and estimate the frequency response of one group of sub-carrier at one time, and synthesize the frequency response of each group to calculate and acquire the compensation coefficient of each transmitting antenna, wherein, the compensation coefficient is used to correspondingly compensate each transmitting antenna. Since the sub-carrier frequency points of the transmitting antenna are regularly grouped, the time domain signal to be transmitted by the transmitting antenna has a certain regularity, therefore, it only needs to select the signal in a corresponding part of time segment therein to transmit during the practical transmission, on the other hand, the time domain signal transmitted by the transmitting antenna in the GP comprises three parts: the first part is filled with zero value to protect the practical calibration signal from being affected by the DwPTS signal; the second part is the selected time domain calibration signal segment; and the third part is also filled with zero value to avoid the mutual interference between the UpPTS signal and the random access signal transmitted in advance.
The preferred example of the present invention will be described in combination with the accompanying figures below, and it should be understood that, the preferred example described here is only used to illustrate and explain the present invention rather than restrict the present invention.
The example of the present invention provides a method for antenna calibration, and FIG. 1 is a flow chart of the method for antenna calibration in accordance with an example of the present invention, and as shown in FIG. 1, the method comprises the following steps:

S102: the transmitting end regularly groups the sub-carrier frequency points of the transmitting antennae and determines the frequency domain calibration pilot signal of each transmitting antenna according to the group, wherein, the transmitting end might comprises one or more transmitting antennae.

Specifically, as shown in FIG. 2, FIG. 2 is a schematic diagram of the transmitting end regularly grouping the sub-carrier frequency points of each transmitting antenna in accordance with an example of the present invention, and the transmitting end regularly groups the sub-carrier frequency points of each transmitting antenna according to FIG. 2. The transmitting end needs to firstly determine the number of groups of grouping sub-carrier frequency points, wherein, the number of total sub-carrier frequency points of the transmitting antenna can be exactly divided by the number of groups, preferably, the number of groups might be 4 or 8. Afterwards, according to the frequency size of the sub-carrier frequency point, the transmitting end groups each sub-carrier frequency point in sequence according to the order from the first group to the last group, and if the number of sub-carrier frequency points is greater than the number of groups, allocate the rest sub-carrier frequency points from the first group to the last group in sequence again. As shown in FIG. 2, suppose that the number of total sub-carrier frequency points is N_ca and the number of groups is M, then allocate the sub-carrier frequency point f₁ to the first group, the sub-carrier frequency point f₂ to the second group, the sub-carrier frequency point f₃ to the third group and so on, the sub-carrier frequency point f_M to the M^th group; restart to allocate to the first group from f _M+ ₁, that is, allocate the sub-carrier frequency point f _M+1 to the first group, the sub-carrier frequency point f_M+2 to the second group, the sub-carrier frequency point f _M+3 to the third group, and the sub-carrier frequency point f_Nca to the M^th group; finally, the transmitting end also needs to determine the number of sub-carrier frequency points in each group, and the number of sub-carrier frequency points in each group is N_ca divided by M.
Wherein, the transmitting end determining the frequency domain calibration pilot signal of each transmitting antenna according to the grouping is specifically: the transmitting end determines the basic sequence according to the number of sub-carrier frequency points in each sub-carrier frequency point group, that is, the length of the basic sequence equals the number of sub-carrier frequency points in each group; and determine the frequency domain calibration pilot signal of each transmitting antenna according to the basic sequence.
In addition, when the transmission calibration is multi-channel simultaneous calibration, the method for generating the frequency domain pilot signal of each transmitting antenna is preferred to be but not limited to the code division multiplexing, wherein, the basic sequence of the code division multiplexing is preferably the Zadoff chu basic sequence.
After step S102, for each sub-carrier frequency point group of one or more transmitting antennae, execute the following steps S104∼S106 on each sub-carrier frequency point group from the first sub-carrier frequency point group.
S104: the transmitting end acquires the time domain integrated calibration pilot signal according to the frequency domain calibration pilot signal, and uses the time domain integrated calibration pilot signal to construct a time domain transmitting signal and send the signal to the receiving end.
Specifically, S104 comprises the following processing:

1. From the first sub-carrier frequency point group, the transmitting end maps the frequency domain calibration pilot signal of each transmitting antenna to the corresponding sub-carrier frequency point in the grouped sub-carrier frequency point group, and fills the positions of the rest unmapped sub-carrier frequency points with zero value to acquire the frequency domain signal of each transmitting antenna;
2. The transmitting end carries out Inverse Fast Fourier Transform (IFFT) on the frequency domain signal of each transmitting antenna to acquire the time domain integrated calibration pilot signal of each transmitting antenna;
3. The transmitting end groups the time domain integrated calibration pilot signal of each transmitting antenna according to the number of groups, for example, if the number of groups is M, the time domain integrated calibration pilot signal of each transmitting antenna is segmented into M segments, and any segment of signal therein is selected as an effective calibration signal;
4. The transmitting end fills zeros before and after the effective calibration signal to construct the time domain transmitting signal of each transmitting antenna; wherein, filling zeros before and after the effective calibration signal can avoid the interference from the DwPTS and the conflict with the UpPTS and the random access signal transmitted in advance, and the length of the filled zeros can be adjusted by changing the number of sub-carrier groups;
5. The transmitting end sends the time domain transmitting signal to the receiving end.

S106: the receiving end receives the time domain transmitting signal in the receiving calibration channel and recovers the time domain integrated calibration pilot signal according to the received time domain transmitting signal.
Preferably, in the condition that there are at least two transmitting antennae, the receiving end superimposes the time domain transmitting signals in a receiving calibration channel to receive; afterwards, the receiving end recovers the time domain integrated calibration pilot signal according to the received time domain transmitting signal and acquires the frequency domain response of each group according to the recovered time domain integrated calibration pilot signal. Specifically, after the transmitting end sends the time domain transmitting signal to the receiving end, the receiving end carries out an operation of removing zeros on the time domain transmitting signal to acquire an effective calibration signal; and use the effective calibration signal to carry out recovery according to the regularity of the time domain integrated calibration pilot signal to acquire the time domain integrated calibration pilot signal of each transmitting antenna.
S108: repeat step 104 to step 106, and after acquiring the time domain integrated calibration pilot signal of each group of each transmitting antenna, convert to the frequency domain signal of the corresponding sub-carrier of each group of each transmitting antenna, and use the relevant algorithm to estimate the frequency responses of corresponding sub-carriers of each group of each transmitting antenna according to the frequency domain pilot of each transmitting antenna.
In step 108, estimating the frequency response of the corresponding sub-carriers of each group of each transmitting antenna comprises but not limited to the following two estimation methods:

1: for each receiving antenna, after superimposing the time domain integrated calibration pilot signal of each group, carry out Fast Fourier Transform (FFT) to convert to the frequency domain signal of the receiving antenna, and then use the relevant algorithm to estimate the frequency response of the corresponding sub-carriers of each group according to the frequency domain pilot of each group in the calibration channel;
2: carry out FFT on the time domain integrated calibration pilot signal of each group of each receiving antenna to convert to the frequency domain signal of the group of the receiving antenna, and then use the relevant algorithm to estimate the frequency response of the corresponding sub-carrier of each group according to the frequency domain pilot of each group.

S110: the receiving end acquires the frequency domain response of all sub-carrier frequency points of each calibration channel according to the frequency domain response of each group.
In S110, the method for synthesizing the estimated frequency response of each sub-carrier group to acquire the frequency response of all sub-carriers of each calibration channel comprises but not limited to the following three synthesizing methods:

1. For each calibration channel, directly combine the estimated frequency responses of the corresponding frequency points of various sub-carrier groups to acquire the frequency response of all sub-carriers;
2. For each calibration channel, and for the estimated frequency response of each sub-carrier group, use the estimated frequency response to interpolate the sub-carrier frequency points without frequency response, and average multiple frequency responses corresponding to each sub-carrier;
3. For each calibration channel, select the estimated frequency response of one sub-carrier group, and use the estimated frequency response to interpolate the sub-carrier frequency points without frequency response, to acquire the frequency response of all sub-carriers.

After S110, it also needs to estimate and smooth the frequency response of the sub-carriers of each calibration channel, and specifically, the transmitting end and receiving end need to repeat the operation of acquiring the frequency domain response of each group and the frequency domain response of all sub-carriers to acquire several frequency domain responses of each sub-carrier; the receiving end averages the several frequency domain responses of each sub-carrier to acquire the average frequency domain response value of each sub-carrier, that is to say, repeat steps S 104-S 108 for N times to acquire N estimated frequency responses of each sub-carrier of each calibration channel, and average n estimated values to acquire the smoothed frequency response of all sub-carriers of each calibration channel.
S112: the receiving end determines the compensation coefficient of each calibration channel according to the frequency domain response of all sub-carriers, wherein, the compensation coefficient is used to correspondingly compensate each calibration channel. Preferably, in the condition of estimating and smoothing the frequency response of the sub-carriers of each calibration channel, the receiving end can determine the compensation coefficient of each calibration channel according to the mean value.
The abovementioned technical scheme of the present invention will be described in detail in combination with examples below.
In related technology, multi-antenna calibration is divided into reception calibration and transmission calibration. Wherein, the transmission calibration is further divided into multi-antenna alternate transmission calibration, multi-antenna simultaneous transmission calibration and multi-antenna group and alternate transmission calibration. The reception calibration means the transmitting end using one antenna to send the calibration pilot signal, and the receiving end receives signal with several antennae at the same time, and each receiving antenna corresponds to one receiving calibration channel to acquire the frequency domain response of the receiving antenna, so as to determine the compensation coefficient. The multi-antenna alternate transmission calibration means that the transmitting end transmits the calibration pilot signal alternately with several transmitting antennae, and only one antenna can be used to transmit the calibration pilot signal at one time, and the receiving end uses one receiving antenna to receive; the transmission calibration of multi-antenna simultaneous calibration means that the transmitting end uses several transmitting antennae to send calibration pilot signals at the same time, and the receiving end uses one receiving antenna to receive the superimposed signal from several transmitting antennae; the multi-antenna group and alternate transmission calibration means dividing the multiple transmitting antennae in the transmitting end into several groups, and each group comprises at least one transmitting antenna, and several groups alternately transmit the calibration pilot signal, and multiple antennae of only one group can transmit the calibration pilot signal simultaneously at one time, and the receiving end uses one receiving antenna to receive the superimposed signal from several transmitting antennae of one group.
From the above description, it can be seen that for the transmitting antenna at each time in the multi-antenna group and alternate transmission calibration and multi-antenna alternate transmission calibration, it is equivalent to the total number of transmitting antennae in the transmission calibration of multi-antenna simultaneous calibration being reduced or 1, thus the multi-antenna group and alternate transmission calibration and multi-antenna alternate transmission calibration can be considered as a special case of the transmission calibration of multi-antenna simultaneous calibration. Moreover, relative to the multi-antenna alternate transmission calibration, the reception calibration is equivalent to a case that the total number of transmitting antennae in the transmission calibration of multi-antenna simultaneous calibration is 1, and there are several receiving antennae.
In the following, take the multi-antenna simultaneous transmission calibration for example to describe the implementation of the technical scheme in detail in combination with FIG. 3:

1. The transmitting end generates the frequency domain calibration pilot signal of each transmitting antenna.

S301: suppose that the total number of sub-carrier frequency points in the transmitting antenna is N_ca, and evenly divide the N_ca into M groups, and the number of sub-carrier frequency points of each group is N_cr, and the allocation method is shown in FIG. 2.
S302: generate a Zadoff_chu basic sequence with a length of N_cr, and the frequency domain calibration pilot signal of each transmitting antenna can be acquired by phase shifting of the basic sequence with different α_i . Suppose that the generated Zadoff_chu basic sequence is r (n), and the frequency domain calibration pilot signal r ⁽ⁱ⁾ (n) of each transmitting antenna might be represented as: $r^{(i)} (n) = e^{j α_{i} n} \overline{r} (n), 0 \leq n < N_{cr}$
Wherein, the phase shifting parameter of each channel: $α_{i} = 2 π \frac{i}{N_{ant}},$
i corresponds to the index number of each transmitting antenna, N_ant controls the phase different of the pilot sequence of each transmitting antenna, N_ant should be greater than the number of transmitting antennae during simultaneous calibration and satisfies N_cr mod N_ant =0.

2. The transmitting end executes the following steps on frequency domain calibration pilot signal of each group according to the group order:

S303: the transmitting end maps the frequency domain calibration pilot signal.
Map the frequency domain calibration pilot signal r ⁽ⁱ⁾ (n) of each transmitting antenna to the corresponding sub-carrier according to the sub-carrier allocation schematic diagram shown in FIG. 2, and the positions of rest sub-carriers are filled with zero value to acquire the frequency domain signal of each transmitting antenna, and the frequency domain signal of the M^th group of the i ^th transmitting antenna is X_{i_m} (k).
S304: the transmitting end segments the time domain integrated calibration pilot signal.
Carry out IFFT on the frequency domain signal X_{i_m} (k) of each transmitting antenna to acquire the corresponding time domain integrated calibration pilot signal x_{i_}m(n). And then segment the time domain integrated calibration pilot signal according to the number of groups, and select any segment of signal as the effective calibration signal to be transmitted. The effective calibration signal sequence y _{i_m}(n) to be transmitted in the i ^th transmitting antenna is: $y_{i_m} (n) = x_{i_m} (n + (q - 1) \times N_{cr} / M), n = 1,2 \dots, N_{cr} / M,$
wherein, q indicates the selected segmental index number.
S305: the transmitting end generates and sends the time domain transmitting signal.
Fill zeros before and after the effective calibration signal sequence y_{i_m} (n) in the selected time domain segment to construct the time domain transmitting signal s_{i_m} (n) of each transmitting antenna and send the signal. s_{i_m} (n) can be denoted as: $s_{i_m} (n) = {\begin{matrix} \begin{array}{l} 0 \\ y_{i_m} (n - N_{DW}) \\ 0 \end{array} & \begin{matrix} n \leq N_{DW} \\ N_{DW} < n \leq N_{cr} / 4 + N_{DW} \\ N_{cr} / 4 + N_{DW} < n \leq N_{GP} \end{matrix} \end{matrix}$
Wherein, N_DW denotes the number of sampling points used to avoid the DwPTS interference time segment, N_GP denotes the number of sampling points in the whole GP.
Changing the number of sub-carrier groups M can change the length of time segment used to avoid the DwPTS interference and also avoid the confliction with the UpPTS and the random access signal transmitted in advance.
S306: the receiving end recovers the time domain integrated calibration pilot signal according to the received time domain signal.
Remove zeros in the received time domain signal $s_{m}^{'}$
(n) to acquire the received effective time domain calibration signal $y_{m}^{'} (n) :$
$y_{m}^{'} (n) = s_{m}^{'} (n) (n + N_{DW}), n = 1,2 \dots, N_{cr} / M$
And then recover the integrated time domain calibration signal $x_{m}^{'} (n)$
according to the regularity of the time domain integrated calibration pilot signal. Take M=4, and q=1 for example, for the first group of pilot signals: $x_{1}^{'} (n) = {\begin{matrix} \begin{array}{l} y_{m}^{'} (n) \\ y_{m}^{'} (n - N_{cr} / 4) \\ y_{m}^{'} (n - N_{cr} / 2) \\ y_{m}^{'} (n - 3 \times N_{cr} / 4) \end{array} & \begin{matrix} n \leq N_{cr} / 4 \\ N_{cr} / 4 < n \leq N_{cr} / 2 \\ N_{cr} / 2 < n \leq 3 \leq N_{cr} / 4 \\ 3 \times N_{cr} / 4 < n \leq N_{cr} \end{matrix} \end{matrix}$
For the second group of pilot signals: $x_{2}^{'} (n) = {\begin{matrix} \begin{array}{l} y_{m}^{'} (n) \\ - Im [y_{m}^{'} (n - N_{cr} / 4)] + jRe [y_{m}^{'} (n - N_{cr} / 4)] \\ - Re [y_{m}^{'} (n - N_{cr} / 2)] - jIm [y_{m}^{'} (n - N_{cr} / 2)] \\ Im [y_{m}^{'} (n - 3 \times N_{cr} / 4)] - jRe [y_{m}^{'} (n - 3 \times N_{cr} / 4)] \end{array} & \begin{matrix} n \leq N_{cr} / 4 \\ N_{cr} / 4 < n \leq N_{cr} / 2 \\ N_{cr} / 2 < n \leq 3 \times N_{cr} / 4 \\ 3 \times N_{cr} / 4 < n \leq N_{cr} \end{matrix} \end{matrix}$
For the third group of pilot signals: $x_{3}^{'} (n) = {\begin{matrix} \begin{array}{l} y_{m}^{'} (n) \\ - y_{m}^{'} (n - N_{cr} / 4) \\ y_{m}^{'} (n - N_{cr} / 2) \\ - y_{m}^{'} (n - 3 \times N_{cr} / 4) \end{array} & \begin{matrix} n \leq N_{cr} / 4 \\ N_{cr} / 4 < n \leq N_{cr} / 2 \\ N_{cr} / 2 < n \leq 3 \times N_{cr} / 4 \\ 3 \times N_{cr} / 4 < n \leq N_{cr} \end{matrix} \end{matrix}$
For the fourth group of pilot signals: $x_{4}^{'} (n) = {\begin{matrix} \begin{array}{l} y_{m}^{'} (n) \\ - Im [y_{m}^{'} (n - N_{cr} / 4)] + jRe [y_{m}^{'} (n - N_{cr} / 4)] \\ - Re [y_{m}^{'} (n - N_{cr} / 2)] - jIm [y_{m}^{'} (n - N_{cr} / 2)] \\ - Im [y_{m}^{'} (n - 3 \times N_{cr} / 4)] + jRe [y_{m}^{'} (n - 3 \times N_{cr} / 4)] \end{array} & \begin{matrix} n \leq N_{cr} / 4 \\ N_{cr} / 4 < n \leq N_{cr} / 2 \\ N_{cr} / 2 < n \leq 3 \times N_{cr} / 4 \\ 3 \times N_{cr} / 4 < n \leq N_{cr} \end{matrix} \end{matrix}$
$j = \sqrt{- 1}$
in all above equations.

3. Acquire the frequency response of each group of each transmitting calibration channel.

S307: the transmitting end estimates the frequency response of each group of each transmitting calibration channel (that is, the channel from each transmitting antenna to calibration receiving antenna).
For the first estimation method, after superimposing the time domain integrated calibration pilot signal of each group, carry out FFT to acquire X'(k), and use the time domain relevant algorithm to estimate the frequency response H_{i_m} (k_m ) of the corresponding sub-carrier of each group of each transmitting calibration channel according to the frequency domain pilot signal of each transmitting calibration channel: $H_{i_m} (k_{m}) = \frac{X' (k_{m})}{r^{(i)} (⌊ k_{m} / M ⌋)}, k_{m} = m, m + M, m + 2 \times M, \dots m + (N_{cr} - 1) \times M$
For the second estimation method, carry out FFT on the recovered integrated time domain calibration signal $x_{m}^{'} (n)$
of each group to acquire $X_{m}^{'} (k),$
and use the time domain relevant algorithm to estimate the frequency response H_{i_m} (k_m ) of the corresponding sub-carrier of each group of each transmitting calibration channel according to the frequency domain pilot signal of each transmitting calibration channel: $H_{i_m} (k_{m}) = \frac{X_{m}^{'} (k_{m})}{r^{(i)} (⌊ k_{m} / M ⌋)}, k_{m} = m, m + M, m + 2 \times M, \dots m + (N_{cr} - 1) \times M$
Preferably, in order to further improve the accuracy of channel estimation, the frequency response H_{i_m} (k_m ) of the sub-carrier can be acquired by further noise reduction processing in time domain.

4. Acquire the frequency response of all sub-carriers of each transmitting calibration channel.

S308: the receiving end synthesizes the frequency responses estimated by various sub-carrier groups to acquire the frequency response H_i (k) of all sub-carriers of each transmitting calibration channel.
For the first synthesizing method: direct combination method: $H_{i} (k) = H_{i_m} (k), k \mod M = m, k = 1,2 \dots N_{ca}$
For the second synthesizing method, firstly interpolate the frequency response H_{i_m} (k_m ) of the existing sub-carriers of each group to acquire the frequency response H_{i_m} (k), k=1,2,...,N_ca of all sub-carriers of this group; and then average the frequency response to acquire the frequency response H_i(k) of all sub-carriers of each transmitting calibration channel among groups: $H_{i} (k) = \frac{1}{M} \sum_{m = 1}^{M} H_{i_m} (k), k = 1,2 \dots, N_{ca}$
For the third synthesizing method, randomly select and interpolate the frequency response H_{i_m} (k_m ) of one group of sub-carriers to acquire the frequency response H_{i_m} (k), k=1,2,...,N_ca of all sub-carriers of this group; and then take the frequency response as the frequency response H_i (k) of all sub-carriers of each transmitting calibration channel.

5. Estimate and smooth the frequency response of sub-carriers of each transmitting calibration channel

S309: acquire N estimated frequency responses for all sub-carriers of each transmitting calibration channel, and average N estimation values to acquire the smoothed frequency response H_{mean_i} (k) of all sub-carriers of each transmitting calibration channel.

6. Calculate the compensation coefficient of each transmitting calibration channel

S310: calculate the compensation coefficient of each transmitting calibration channel according to the smoothed frequency response, and correspondingly compensate each transmitting calibration channel according to the compensation coefficient to make the frequency responses of the transmitting channels consistent. Acquire the mean value of the maximum power $P = \frac{1}{K} \sum_{i = 1}^{K_{a}} \max_{k} ({| H_{mean_i} (k) |}^{2})$
of each transmitting calibration channel, and the compensation coefficient in each channel is: $C_{i} (k) = \frac{sqrt (P)}{H_{mean_i} (k)}$
Use the corresponding compensation coefficient to compensate the transmitted data to achieve the antenna transmitting calibration function.
In addition, for multi-antenna alternate transmission calibration, the transmitting end uses each transmitting antenna to alternately execute step 305 for sending the calibration signal, and the receiving end repeats executing S306 and S307 at the corresponding time, and estimates the frequency response of each group of each transmitting calibration channel (that is, the channel from each transmitting antenna to calibration receiving antenna).
For multi-antenna group and alternate transmission calibration, the transmitting end uses each group of transmitting antennae to alternately execute step 305 for sending the calibration signal, and the receiving end repeats executing S306 and S307 at the corresponding time, and estimates the frequency response of each group of transmitting calibration channels in each group (that is, the channels from each group of transmitting antennae to calibration receiving antenna).
For the reception calibration, each receiving antenna in the receiving end concurrently executes S306 and S307, and estimates the frequency response of each group of each corresponding receiving calibration channel (that is, the channel from the calibration antenna to each receiving antenna).
The present invention also provides a system for antenna calibration, as shown in FIG. 4 that is a block diagram of the system for antenna calibration in accordance with an example of the present invention, the system for antenna calibration in accordance with an example of the present invention comprises: a transmitting end 40, for example a transmitter; and a receiving end 42, for example a receiver. Wherein, the transmitting end 40 comprises: a frequency domain calibration pilot sequence generation unit 401, a frequency domain calibration pilot sequence mapping unit 402, a first conversion unit 403, and a time domain transmitting signal generation unit 404; the receiving end 42 comprises a time domain integrated calibration pilot recovery unit 420, a second conversion unit 421, a sub-carrier frequency response estimation unit 422, a channel frequency response synthesizing unit 423, a channel frequency response smoothing unit 424, and a compensation coefficient determination unit 425. In the following, the abovementioned units will be described in detail in combination with FIG. 4.
The frequency domain calibration pilot sequence generation unit 401 connects to the frequency domain calibration pilot sequence mapping unit 402, and is used to group at least one, that is the sub-carrier frequency points of at least one transmitting antenna and determine the frequency domain calibration pilot signal of at least one transmitting antenna according to the group.
The frequency domain calibration pilot sequence mapping unit 402 connects to the first conversion unit 403 and is used to map the frequency domain calibration pilot signal to the corresponding grouped sub-carrier frequency points to acquire the frequency domain signals of at least one transmitting antenna.
The first conversion unit 403 connects to the time domain transmitting signal generation unit 404 and is used to convert the frequency domain signal to the time domain integrated calibration pilot signal of at least one transmitting antenna by IFFT.
The time domain transmitting signal generation unit 404 is used to segment the time domain integrated calibration pilot signal and select any segment of signal as the effective calibration signal, and construct the time domain transmitting signals of at least one transmitting antenna.
The time domain integrated calibration pilot recovery unit 420 is used to restore the time domain transmitting signal to the time domain integrated calibration pilot signal.
The second conversion unit 421 is used to convert the time domain integrated calibration pilot signal to the frequency domain calibration pilot signal.
The sub-carrier frequency response estimation unit 422 is used to determine the frequency domain response of each group according to the frequency domain calibration pilot signal.
The channel frequency response synthesizing unit 423 is used to determine the frequency domain responses of all sub-carrier frequency points of at least one calibration channel according to the frequency domain response of each group.
The channel frequency response smoothing unit 424 is used to average the frequency domain responses of all sub-carrier frequency points of at least one calibration channel which are acquired many times to acquire the mean value of the frequency domain responses of all sub-carriers of at least one calibration channel.
The compensation coefficient determination unit 425 is used to determine the compensation coefficient of at least one calibration channel according to the mean value of multiple calibration channels.
In the following, the processing procedure of the system for antenna calibration performing antenna calibration is described in detail.
Firstly, the frequency domain calibration pilot sequence generation unit 401 determines the number of sub-carrier groups of the transmitting antenna and generates a frequency domain pilot sequence; the frequency domain calibration pilot sequence mapping unit 402 maps the pilot sequence to the corresponding sub-carrier according to the group index set during the grouping, and sends the mapped frequency domain calibration signal to the first conversion unit 403; the first conversion unit 403 carries out IFFT on the frequency domain signal of each transmitting antenna to convert to the time domain for acquiring the time domain integrated calibration pilot signal and sends the signal to the time domain transmitting signal generation unit 404; in the time domain transmitting signal generation unit 404, segment the time domain integrated calibration pilot signal in each transmitting antenna, and randomly select one segment and fills zeros before and after the segment to construct the time domain transmitting signal with GP time length and sends it to the transmitter to send.
In the transmitter, the signals in each transmitting antenna are sent individually, and in the receiver, receive the superimposed time domain transmitting signal transmitted by at least one transmitting antenna, and send the signal to the time domain integrated calibration pilot recovery unit 420; remove zeros from the received signal in the time domain integrated calibration pilot recovery unit 420, and use the regularity of grouping to recover the time domain integrated calibration pilot and sends the pilot to the second conversion unit 421; the second conversion unit 421 converts the recovered time domain integrated calibration pilot signal to the frequency domain signal and sends the frequency domain signal to the sub-carrier frequency response estimation unit 422; use the relevant algorithm to estimate the frequency response at the position of the corresponding sub-carrier of at least one calibration channel in the sub-carrier frequency response estimation unit 422, and send the estimated frequency response to the channel frequency response synthesizing unit 423; the channel frequency response synthesizing unit 423 synthesizes the estimated frequency response of each group in the buffer into the frequency response at the position of all sub-carriers of at least one calibration channel, and sends the frequency response to the channel frequency response smoothing unit 424; the channel frequency response smoothing unit 424 smoothes the frequency responses of all sub-carriers of at least one calibration channel which are acquired many times in the buffer to acquire a smoothed frequency response of all sub-carriers of at least one calibration channel, and sends the frequency response to the compensation coefficient determination unit 425; calculate the compensation coefficient of at least one calibration channel in the compensation coefficient determination unit 425.
To sum up, with the technical scheme of the present invention, use a way of grouping sub-carriers to construct a regular time domain calibration pilot signal to reduce the calibration pilot time domain transmitting time length, so as to solve the problem that the calibration detection pilot signal interferes with the normal communication of the communication system in the prior art, thus the transmission of the antenna calibration pilot signal can avoid the influence from the DwPTS and the UpPTS and improve the calibration estimation precision without affecting the normal communication.
The above description is only a preferred example rather than a restriction of the present invention, and for those skilled in the field, there are different modifications and changes without departing from the scope of the present invention as defined by the appended claims.

Claims

A method for antenna calibration, wherein the method comprises:
a transmitting end grouping sub-carrier frequency points in a transmitting antenna and determining a frequency domain calibration pilot signal of the transmitting antenna according to the grouping (S102);

the transmitting end acquiring a time domain integrated calibration pilot signal according to the frequency domain calibration pilot signal, and using the time domain integrated calibration pilot signal to construct a time domain transmitting signal and sending the time domain transmitting signal to a receiving end (S104);

the receiving end restoring the received time domain transmitting signal to the time domain integrated calibration pilot signal (S106);

the receiving end acquiring a frequency domain response of each group according to the time domain integrated calibration pilot signal (SI08), and acquiring frequency domain responses of all sub-carrier frequency points in a calibration channel according to the frequency domain response of each group (S110);

the receiving end determining a compensation coefficient of the calibration channel according to the frequency domain responses of all sub-carriers (S112);

wherein, the transmitting end acquires the time domain integrated calibration pilot signal according to the frequency domain calibration pilot signal, and uses the time domain integrated calibration pilot signal to construct the time domain transmitting signal and sends the time domain transmitting signal to the receiving end, specifically comprising:
the transmitting end mapping the frequency domain calibration pilot signals to grouped corresponding sub-carrier frequency points, and filling locations of the rest unmapped sub-carrier frequency points with zero value to acquire a frequency domain signal of the transmitting antenna;

the transmitting end converting the frequency domain signal of the transmitting antenna to the time domain integrated calibration pilot signal of the transmitting antenna;

the transmitting end segmenting the time domain integrated calibration pilot signal of the transmitting antenna according to the number of groups, and selecting any segment of signal therein as an effective calibration signal;

the transmitting end carrying out an operation of filling zeros before and after the effective calibration signal to construct the time domain transmitting signal of the transmitting antenna;

the transmitting end sending the time domain transmitting signal to the receiving end.
The method of claim 1, wherein the transmitting end grouping the sub-carrier frequency points in the transmitting antenna specifically comprises:
the transmitting end grouping the sub-carrier frequency points in at least one transmitting antenna.
The method of claim 2, wherein when there are at least two said transmitting antennae, after the transmitting end sends the time domain transmitting signal to the receiving end, the method further comprises:
the receiving end superimposing the time domain transmitting signals in one receiving calibration channel to receive.
The method of claim 3, wherein the transmitting end groups the sub-carrier frequency points in the transmitting antenna, specifically comprising:
determining a number of groups of grouping the sub-carrier frequency points;

grouping each sub-carrier frequency point in an order from first group to last group in sequence according to frequency sizes of the sub-carrier frequency points, and if the number of the sub-carrier frequency points is greater than the number of groups, allocating the rest sub-carrier frequency points in sequence from the first group to the last group again;

determining the number of the sub-carrier frequency points in each group.
The method of claim 4, wherein a total number of the sub-carrier frequency points is exactly divided by the number of the groups.
The method of claim 5, wherein the number of the groups is 4 or 8.
The method of claim 4, wherein the transmitting end determines the frequency domain calibration pilot signal of the transmitting antenna according to the grouping, specifically comprising:
the transmitting end determining a basic sequence according to the number of the sub-carrier frequency points in each group, and determining the frequency domain calibration pilot signal of the transmitting antenna according to the basic sequence.
The method of claim 7, wherein when carrying out multi-channel simultaneous transmission calibration, the method also comprises:
the transmitting end using a way of code division multiplexing to determine the frequency domain calibration pilot signal of each calibration channel.
The method of claim 8, wherein a pilot sequence of the code division multiplexing is Zadoff_chu basic sequence.
The method of claim 1, wherein the receiving end recovering the time domain integrated calibration pilot signal according to the received time domain transmitting signal comprises:
the receiving end carrying out an operation of removing zeros on the time domain transmitting signal to acquire the effective calibration signal;

the receiving end carrying out recovery processing on the effective calibration signal to acquire the time domain integrated calibration pilot signal.
The method of claim 10, wherein the receiving end acquiring the frequency domain response of each group according to a recovered time domain integrated calibration pilot signal comprises:
the receiving end converting the recovered time domain integrated calibration pilot signal to the frequency domain signal;

the receiving end acquiring the frequency domain response of each group in the calibration channel according to a frequency domain pilot of each group in the calibration channel.
The method of claim 11, wherein the receiving end acquiring the frequency domain response of each group according to the recovered time domain integrated calibration pilot signal further comprises:
for each receiving antenna, after superimposing the time domain integrated calibration pilot signal of each group, the receiving end performing Fast Fourier Transform to convert to the frequency domain signal of the receiving antenna, and estimating frequency responses of corresponding sub-carriers of each group in the calibration channel according to the frequency domain pilot of each group in the calibration channel;

or, the receiving end carrying out Fast Fourier transform on the time domain integrated calibration pilot signal of each group of each receiving antenna to convert to the frequency domain signal of each group of the receiving antenna, and estimating the frequency responses of the corresponding sub-carriers of each group according to the frequency domain pilot of each group.
The method of claim 12, wherein the receiving end acquiring the frequency domain responses of all sub-carrier frequency points according to the frequency domain response of each group comprises:
the receiving end directly combining the frequency domain responses of corresponding frequency points of various sub-carrier frequency point groups for each calibration channel to acquire the frequency domain responses of all sub-carriers; or,

for each calibration channel, the receiving end using a determined frequency response to interpolate sub-carrier frequency points without frequency responses for the frequency response of the sub-carrier frequency points in each group, and averaging a plurality of frequency responses corresponding to each sub-carrier frequency point to acquire the frequency domain responses of all sub-carriers; or,

the receiving end selecting the frequency response of sub-carrier frequency points in one group for each calibration channel and using the determined frequency response to interpolate the sub-carrier frequency points without frequency responses to acquire the frequency domain responses of all sub-carriers.
The method of claim 13, wherein after the receiving end acquires the frequency domain responses of all sub-carriers according to the frequency domain response of each group, the method also comprises:
the receiving end repeating the operation of acquiring the frequency domain response of each group and the frequency domain response of all sub-carriers to acquire a plurality of frequency domain responses of all sub-carriers;

the receiving end carrying out an average operation on said a plurality of frequency domain responses of all sub-carriers to acquire a mean value of said a plurality of frequency domain responses of all sub-carriers.
The method of claim 14, wherein the receiving end determining the compensation coefficient of the calibration channel according to the frequency domain responses of all sub-carriers comprises:
the receiving end determining the compensation coefficient of the calibration channel according to the mean value.
The method of claim 15, wherein after the receiving end determines the compensation coefficient of the calibration channel according to the mean value, the method also comprises:
the receiving end correspondingly compensating the calibration channel according to the compensation coefficient.
A system for antenna calibration, the system comprises a transmitting end (40) and a receiving end (42), wherein,
the transmitting end (40) is used to group sub-carrier frequency points in a transmitting antenna and determine a frequency domain calibration pilot signal of the transmitting antenna according to the group; and acquire a time domain integrated calibration pilot signal according to the frequency domain calibration pilot signal and use the time domain integrated calibration pilot signal to construct a time domain transmitting signal and send the time domain transmitting signal to the receiving end (42);
the receiving end (42) is used to restore the received time domain transmitting signal to the time domain integrated calibration pilot signal, and acquire a frequency domain response of each group according to the time domain integrated calibration pilot signal, and acquire the frequency domain response of all sub-carrier frequency points of a calibration channel according to the frequency domain response of each group, and determine a compensation coefficient of the calibration channel according to the frequency domain response of all sub-carriers;
wherein, the transmitting end (40) is used to acquire the time domain integrated calibration pilot signal according to the frequency domain calibration pilot signal, and use the time domain integrated calibration pilot signal to construct the time domain transmitting signal and send the time domain transmitting signal to the receiving end (42) by the following way:
mapping the frequency domain calibration pilot signals to grouped corresponding sub-carrier frequency points, and filling locations of the rest unmapped sub-carrier frequency points with zero value to acquire a frequency domain signal of the transmitting antenna;

converting the frequency domain signal of the transmitting antenna to the time domain integrated calibration pilot signal of the transmitting antenna;

segmenting the time domain integrated calibration pilot signal of the transmitting antenna according to the number of groups, and selecting any segment of signal therein as an effective calibration signal;

carrying out an operation of filling zeros before and after the effective calibration signal to construct the time domain transmitting signal of the transmitting antenna; and

sending the time domain transmitting signal to the receiving end (42).
The system of claim 17, wherein the transmitting end comprises:
a frequency domain calibration pilot sequence generation unit (401) used to group the sub-carrier frequency points of at least one transmitting antenna and determine the frequency domain calibration pilot signal of said at least one transmitting antenna according to the group;

a frequency domain calibration pilot sequence mapping unit (402), used to map the frequency domain calibration pilot signal to a grouped corresponding sub-carrier frequency point to acquire a frequency domain signal of said at least one transmitting antenna;

a first conversion unit (403), used to convert the frequency domain signal to the time domain integrated calibration pilot signal of said at least one transmitting antenna;

a time domain transmitting signal generation unit (404) used to segment the time domain integrated calibration pilot signal, and select any segment of signal therein as an effective calibration signal and construct the time domain transmitting signal of said at least one transmitting antenna.
The system of claim 17 or 18, wherein the receiving end comprises:
a time domain calibration pilot recovery unit (420), used to restore the time domain transmitting signal to the time domain integrated calibration pilot signal;

a second conversion unit (421), used to convert the time domain integrated calibration pilot signal to the frequency domain signal;

a sub-carrier frequency response estimation unit (422), used to determine the frequency domain response of each group according to the frequency domain signal;

a channel frequency response synthesizing unit (423), used to determine the frequency domain responses of all sub-carrier frequency points in at least one calibration channel according to the frequency domain response of each group;

a channel frequency response smoothing unit (424), used to carry out an average operation on the frequency domain responses of all sub-carrier frequency points of at least one calibration channel which are acquired many times to acquire a mean value of the frequency domain responses of all sub-carriers of at least one calibration channel;

a compensation coefficient determination unit (425), used to determine the compensation coefficient of at least one calibration channel according to the mean value of a plurality of calibration channels.